The Future of Downhole Drilling Tool Selection
by descending suitability, thus revealing the optimal designs towards the top of the screen. Using this software, the optimal reamer can be defined, following which the optimally matched bit can be selected.
Rotary Steerable Matcher
The rotary steerable matcher is primarily a specialist interface for a database that contains logic tables. For each and every commercial rotary steerable tool, a logic table has been created, which in essence is a matrix of trajectory requirement against key characteristics of the drill bit. The latter includes:
• length of the drill bit;
• gauge length; • • •
gauge design, including cutting structure, profile and geometry; presence or absence of a full or partial ring gauge;7 presence or absence of a tapered gauge;8
and • side-cutting index.
Due to the vast diversity of features required to accomplish the optimal matched concept, there are over 20 drill-bit variables assessed within the logic tables, not including the factors that are encapsulated within the side-cutting index calculation. The trajectory requirement in the matrix is segmented into multiple options to provide the comprehensive range of directional objectives in which rotary steerable tools are employed.
Aside from the segmentation by dogleg requirement (high, medium and low), it also includes specific objectives, such as kick-off from vertical and open-hole sidetracks. The effect of hole angle is also incorporated within the matrix, with options existing for drilling at differing degrees of inclination, as well as vertical sections with varying bed dip angles.
For each individual variation in both drill bit characteristic and trajectory option, a number is entered into the matrix. This number depicts the degree to which the feature matches the trajectory for the specific rotary steerable tool. A high score represents an ideal match, whereas a zero score represents incompatibility. The number is a result of:
•
intensive communication, research and testing with the directional tool providers;
• mathematical modelling; •
• •
development of innovative features and technologies for specific tools;
analysis of the thousands of runs accumulated; and use of field verification tools and techniques.
The logic tables are linked to an interface that allows the user to enter three sets of search criteria (see Figure 4): bit size, the specific rotary steerable tool utilised and the well profile. Once defined, the search function can commence. This links the specific logic table to the drill-bit characteristics for the entire fixed-cutter product line. For each defined characteristic of the drill bit, a number is provided from the logic table that correlates to its suitability to the specific tool and trajectory. The search results generated provide a list of all the drill bits of that size, with their corresponding total score expressed as a percentage.
A tool that is capable of calculating the four indices for a bit allows optimal bits to be developed for application once the importance rankings are defined for that application.
The user will have a number of drill bit designs returned by the selection tool. They are arranged in rows, with each row detailing an individual product or version. These rows are sorted by descending suitability, thus revealing the optimal designs towards the top of the screen.
Conclusions
There are four indices that substantially describe the performance of a bit: ROP, stability, durability and steerability. Bits that look similar to one other often perform very differently. Bit selection based on indices gives much more appropriate bit recommendations than ‘conventional wisdom’ selection based on coarser, visible measures such as number of blades or cutter size. A tool that is capable of calculating the four indices for a bit allows optimal bits to be developed for application once the importance rankings are defined for that application. However, the indices interact with each other in ways that are mainly intuitive the calculation of quantitative indices allows these interactions to be very accurately understood so that bits can be optimised for specific applications.
The suitability of bits for specific drilling tools can be assessed using a sophisticated matcher tool. These can be tailored, via user input, to the specific parameters of the application. The matching tool provides a logical and quantitative approach to bit selection for drilling tools. n
1.
Johnson S, A new method of producing laterally stable PDC drill bits, paper IADC/SPE 98986 presented at the 2006 Society of Petroleum Engineers/International Association of Drilling Contractors Drilling Conference, Miami, 21–23 February 2006.
2.
Barton S, Development of stable PDC bits for specific use on rotary steerable systems, paper IADC/SPE 62779 presented at the 2000 Society of Petroleum Engineers/International Association of Drilling Contractors Asia Pacific Drilling Conference, Kuala Lumpur, 11–13 September 2000.
3.
Clegg J, Barton S, Improved opptimization of bit selection using mathematically modeled bit performance indices, paper IADC/SPE 102287 presented at the 2006 Society of Petroleum Engineers/International Association of Drilling
Contractors Asia Pacific Drilling Technology Conference, Bangkok, 13–15 November 2006.
4.
Barton S, Gee R, Murdock A, Novel selection tool enables scientific approach to matched assemblies, paper IADC/SPE 128197 presented at the 2010 Society of Petroleum Engineers/International Association of Drilling Contractors Drilling Conference, New Orleans, 2–4 February 2010.
5.
Barton S, Weeden R, Accurate matching of bit and reamer tools delivers optimized drilling performance, paper SPE 132057 presented at the 2010 Center for Petrolium Studies/Society of Petroleum Engineers International Oil and Gas Conference, Beijing, 8–10 June 2010.
6.
Barton S, Card K, Nwachukwu D, et al., Bit selection using mathematically modeled indices deliver significant
7.
improvement in directional drilling performance, paper OTC 19915 presented at the 2009 Offshore Technology Conference, Houston, TX, 4–7 May 2009.
Roberts T, Development of a new concept of steerable PDC bit for directional drilling, paper IADC/SPE 39307 presented at the 1998 Society of Petroleum Engineers/International Association of Drilling Contractors Drilling Conference, Dallas, 3–6 March 1998.
8.
Niznik MR, et al., A new approach to stick-slip management integrating bit design and rotary-steerable-system characteristics, paper IADC/SPE 98962 presented at the 2006 Society of Petroleum Engineers/International Association of Drilling Contractors Drilling Conference, Miami, 21–23 February 2006.
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EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 2
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